黄土高原坡耕地沟蚀土壤质量评价

黄土高原坡耕地沟蚀广泛而严重。科学评价沟蚀土壤质量是侵蚀环境下土壤保育和利用的重要基础。论文以沟间土壤为对照,分析了坡耕地沟蚀对土壤质量单因子的影响并建立了沟蚀土壤质量综合评价模型。利用加权和法对黄土高原坡耕地不同沟蚀深度下土壤质量进行综合评价。结果表明：①沟蚀对坡耕地不同土壤质量因子的影响有较大差异。沟蚀导致土壤硬化,pH值增加,而土壤团聚体和养分含量（除全磷）随着沟蚀深度增加表现出明显的层次性,近似呈＂W＂型变化规律。②沟蚀深度对土壤质量的影响可以用幂函数y=0.866 8 x-0.142（R2=0.877）较好地拟合。微度侵蚀（〈5 cm）、中度侵蚀（5～30 cm）和重度侵蚀（30～50 cm）的土壤质量指数较沟间土壤分别降低了10.6%、27.9%和36.5%。沟蚀深度5 cm和30 cm是土壤质量显著下降的两个关键点。③反映沟蚀土壤质量的指标可以归为肥力因子、质地因子和结构因子三类。土壤有机质、水稳性团聚体、土壤比表面积和容重4项指标能够很好地反映土壤质量状况,可作为坡耕地沟蚀土壤质量的表征指标。

Gully Erosion Soil Quality Assessment on the Cultivated Slope Land in the Loess Plateau Region,China

Characterized by dry climate,concentrated rainfall and fragile soil,the Loess Plateau has experienced serious soil erosion for long time.Gully erosion of cultivated slope land is wide and serious,which has led to tremendous soil and nutrient losses as well as production reduction.However,the effect of gully erosion on soil degradation hasn’t been paid enough attention from the managers and agricultural scientists because soil degradation is a gradual process and might not ostensibly lead to a serious loss of agricultural production.It’s still not quite clear about the effect of gully erosion on soil attributes and soil quality on the Loess Plateau.In the present study,the soil in the inter-gully was chosen to be the control soil.Sixty-four profiles,with various erosion depths were selected and 16 soil physiochemical indicators were determined in gully and inter-gully soil.Subsequently,a comprehensive assessment model was established through analyzing the effect of gully erosion on soil quality factors.Using principal component analysis(PCA) and stepwise discriminant analysis,the soil quality evolution under different gully erosion depths was evaluated quantitatively with weighted integrated method of PCA.The result showed that the effect of gully erosion on soil quality indicators was different in the cultivated slope land.In detail,gully erosion would harden the surface soil and increase pH value,while the changes of soil water-stable aggregate and nutrient content showed an obvious hierarchy with increment of gully erosion depth.The change law presents a "W shaped" pattern.The relationship between gully erosion and soil quality index(SQI) could be preferably fitted by the power function curve of y=0.8668 x-0.142(R2=0.877).Therefore,the SQI under the condition of low erosion intensity(<5 cm),moderate erosion intensity(5-30 cm) and high erosion intensity(30-50 cm) reduced 10.6%,27.9% and 36.5%,respectively as compared with the control soil.It was noted that the SQI under moderate erosion intensity was 17.3% lower than that of low erosion intensity while about 8.6% higher than that of high erosion intensity.Thus,the erosion depths of 5 cm and 30 cm were the two critical points where the SQI reduced significantly.Besides,the soil quality indicators that could well responded to the gully erosion in the cultivated slope land could be classified into soil fertilizer indicator,texture indicator and structure indicator.Moreover,four soil quality indicators including soil organic matter,soil specific surface area,soil aggregate content and soil bulk density were identified as the most sensitive and simplified indicators for evaluating soil quality influenced by gully erosion in the cultivated slope land on the Loess Plateau.